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Authors , , and

Abstract

Objective

To document intrastrain variation of lipopolysaccharide (LPS) in Pasteurella multocida and correlate these changes with changes in determinants associated with virulence.

Animals

25 broad-breasted white turkeys.

Procedure

Phenotypic bacterial variants were identified by lectin affinity and were assayed for adherence to epithelial cells and complement resistance in vitro. The LPS purified from these variants was subjected to polyacrylamide gel electrophoresis and lectin affinity analysis. Turkeys were challenge exposed, then observed for 1 week. At first sign of disease, or at the end of the study, turkeys were euthanatized, necropsied, and inspected for gross lesions.

Results

The LPS variant designated as Ricinus communis agglutinin-positive had greater adherence to epithelial cells, complement resistance, and virulence in turkeys than did the variant designated as R communis agglutinin-negative.

Conclusions

Intrastrain variation of LPS exists in P multocida, and changes in LPS are correlated with changes in virulence. (Am J Vet Res 1997;58:755–759)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the pathogenic potential of an adenovirus isolated from a goat.

Animals

14 colostrum-deprived, isolation-reared goat kids approximately 3 weeks old.

Procedure

Kids were inoculated with either cell culture fluid containing adenovirus (n = 10) or uninfected cell culture fluid (n = 4): 2 ml transtracheally and 1 ml/nostril. Clinical signs of disease and rectal temperature were recorded daily; nasal secretion and fecal specimens were collected daily. Control kids were necropsied, 2/d, on postinoculation days (PID) 5 and 10. Virus-inoculated kids were necropsied on PID 3, 5, 7, 10, and 28. After necropsy, lung, liver, kidney, and brain specimens were aseptically collected for virus isolation attempts. Tracheal fluid was collected on sterile cotton swabs. Turbinate, trachea, lung, mediastinal lymph node, liver, kidney, duodenum, jejunum, ileum, mesenteric lymph node, colon, and brain specimens were collected for histologic evaluation.

Results

Kids developed mild-to-moderate clinical respiratory tract infection. Virus was recovered consistently from nasal secretion and sporadically from fecal specimens. Grossly, there were multiple areas of atelectasis and hyperemia, principally in the cranioventral portion of the lungs. Microscopically, there was detachment and sloughing of foci of epithelial cells of the terminal bronchioles and alveoli. In kids necropsied late in the disease, these changes were accompanied by hyperplasia of type-II epithelial cells. Viral inclusions were not an obvious feature, but a few cells contained probable inclusions.

Conclusions and Clinical Relevance

The caprine adenovirus reported here is capable of inducing respiratory tract disease and lesions in the lungs of young kids. (Am J Vet Res 1997;58:608–611)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To develop a reference database for characterization of bovine Staphylococcus aureus and Streptococcus agalactiae strains by automated ribotyping and to use it to assess the discriminatory power of this typing procedure and the geographic distribution of Sta aureus and Str agalactiae strains in New York state dairy herds.

Sample Population

22 commercial dairy herds.

Procedure

Isolates of Sta aureus and Str agalactiae from bovine milk were identified by standard bacteriologic procedures, then typed by automated ribotyping. Antimicrobial susceptibility of isolates was tested in vitro. Two indicators made from the data were percentage of farms with multiple ribotypes and percentage of single ribotypes found in several geographic regions. Standard bacteriologic diagnosis, automated ribotyping, and determination of antibiograms (Kirby-Bauer method) also were done.

Results

Of 50 Sta aureus and 44 Str agalactiae isolates from composite milk samples of 12 and 10 herds, respectively, 18 and 14 ribotypes, respectively, were identified. The discriminatory power of automated ribotyping was approximately 0.96 (Hunter-Gaston's formula). A higher percentage of herds with Sta aureus had multiple ribotypes. The most common Sta aureus ribotypes tended to have broader geographic distribution. Some Sta aureus ribotypes were significantly associated with antibiotic resistance profiles.

Conclusions

Automated ribotyping appears to characterize bovine strains of bacteria associated with intramammary infections with a high discriminatory index. Potential applications include identification of strains that appear to have broad geographic distribution suggesting interfarm transfer, discrimination between recurrent versus new intramammary infections (ie, for control of Str agalactiae and Sta aureus), and evaluation of antibiotic therapy. (Am J Vet Res 1997;58:482–487)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate whether heparin has any effect on the growth of porcine reproductive and respiratory syndrome virus (PRRSV).

Sample Population

2 isolates of PRRSV, and as control viruses, 1 isolate of pseudorabies virus (PRV) and 1 isolate of parainfluenza 3 virus (PIV-3).

Procedures

Plaque assays, using a continuous cell line (MARC-145) derived from African green monkey kidney cell line (MA104), were performed for determination of inhibitory effect of heparin on PRRSV, PRV, and PIV-3. The effect of various doses of heparin and heparinase on the growth of PRRSV, PRV, and PIV-3 was evaluated and compared. In each experiment, values were expressed as the mean value for duplicate samples.

Results

The number of plaques formed by PRRSV and PRV was reduced to 24 to 25 and 15% of the untreated control (100%), respectively, by 1 U of heparin/ml, but could not be reduced below 6 to 7 and 3%, respectively, by use of concentrations up to 50 U/ml. An inhibitory effect of heparin, at a concentration up to 50 U/ml, was not observed on PIV-3. Delaying addition of heparin for 30 minutes after the addition of PRRSV and PRV reduced plaque formation by 48 to 51 and 68%, respectively, compared with 91 to 92 and 95%, respectively, if heparin was added at the time of infection. In addition, most PRRSV added was retained by heparin beads, as was PRV. Heparinase treatment of MARC-145 cells reduced the number of PRRSV-, as well as PRV-induced plaques. On the other hand, the number of PIV-3-induced plaques did not decrease after treatment of MARC-145 cells with heparinase.

Conclusions

Addition of heparin to PRRSV or to the MARC-145 cells before virus inoculation and treatment of the cells with heparinase prevented the virus from infecting the cells. (Am J Vet Res 1997;58:488–491)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the apparent molecular weight for 24 ruminant respiratory syncytial viruses (RSV) on the basis of differences in the electrophoretic mobility of the phosphoprotein (P protein).

Procedure

29 bovine RSV (BRSV), 20 of which were not previously tested, 3 ovine RSV, and 1 caprine RSV isolates were selected for determination of electrophoretic mobility of the P protein. Virus radiolabeled with [35S]methionine was immunoprecipitated with polyclonal antiserum to BRSV and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Results

On the basis of apparent molecular size of the P protein, all isolates could be categorized into 2 electropherotypes, low molecular size of 36 kd and high molecular size of 38 kd. Twenty-three BRSV, the 3 ovine RSV, and 1 caprine RSV isolates had a high molecular size P protein; 6 BRSV isolates had a low molecular size P protein.

Conclusions

The apparent molecular size of the P protein of the ruminant RSV strains is greater than that of the human RSV subgroups, providing further evidence of their distinctiveness. Whether categorization of electrophoretic mobility of the P protein of BRSV underlies distinct antigenic subgroups, as it does in human RSV, requires further antigenic and genetic analysis.

Clinicai Relevance

Antigenic subgroups of ruminant RSV may have relevance in the development of new vaccines for control of the disease. (Am J Vet Res 1997;58:478–481)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine persistence of bacteremia, pathogenicity, and immunoglobulin kinetics after blood transmission of Bartonella henselae in cats.

Animals

18 specific-pathogen-free (SPF) cats (16 weeks old) received blood or urine from 4 adult cats (2 SPF, 2 naturally infected with B henselae).

Procedure

SPF cats were inoculated with blood IV (n = 4), blood IM (n = 4), or urine sediment IM (n = 4) from 2 bacteremic cats (donors A and B). Control cats (2/route) received inoculum from culture-negative, seronegative SPF cats (donors C and D).

Results

6 cats (5 blood, 1 urine) were transiently febrile during the 213-day observation period. Two bacteremic cats developed CNS abnormalities. Transient anemia was the only hematologic abnormality. Bacteremia was induced in 7 of 8 blood recipients by postinoculation day (PID) 11. Urine recipients (n = 6) did not become bacteremic or seroconvert by PID 108, but when challenge exposed IV with blood, 4 of 6 became infected. All infected cats developed relapsing bacteremia. Initially, colony counts for donor-A recipients were 103 greater than those for donor-B recipients; however, during relapses, counts were similar. Polymerase chain reaction-restriction fragment length polymorphism analysis of 16S rRNA gene and the intergenic spacer region revealed no differences among isolates derived from recipient cats. Bartonella henselae-specific antibodies were detected between PID 15 and 18 in donor-A, compared with PID 46 and 181 in donor-B recipients. The peak geometric mean titer of donor-A recipients was 1,448, versus 406 for donor-B recipients.

Conclusions and Clinical Relevance

Blood transmission of B henselae induced subtle clinical abnormalities; the biological behavior of the 2 donor strains differed; and relapsing bacteremia can persist in conjunction with variably high antibody titers. (Am J Vet Res 1997;58:492–497)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To protect cats by inoculating them intratracheally with feline infectious peritonitis virus (FIPV), followed by a second inoculation with virus propagated at reduced temperatures.

Animals

Twelve 12-week-old, specific-pathogen-free kittens.

Procedure

Ten to 400,000 plaque-forming units (PFU) of virulent (low passage) FIPV, strain FIPV-1146 were inoculated intratracheally, followed by intranasal inoculation with high-passage FIPV-1146 (104 to 106, TCID50) on day 133. Cats were allotted to 2 groups and challenge exposed on day 188 by aerosolization of either virulent FIPV-1146 or FIPV-UCD1.

Results

Two of the 3 severely affected kittens, given 3 dosages intratracheally, were euthanatized. The third kitten recovered. A serologic response was not detected in cats inoculated with 100 PFU or less and in 1 of 2 cats given 1,000 PFU. Clinical signs of infection were not observed in surviving cats after intranasal inoculation with high-passage FIPV-1146 133 days after the initial dose. All cats seroconverted. Aerosol challenge exposure of all kittens with either virulent FIPV-1146 or FIPV-UCD1 caused no adverse effects except in kittens previously affected after the first inoculation. Residual lesions of FIPV were observed histologically.

Conclusions and Clinical Relevance

There appeared to be a beneficial effect clinically by intratracheal/intranasal inoculation, but not complete protection, as observed histologically. (Am J Vet Res 1997; 58:251–256)

Free access
in American Journal of Veterinary Research
Authors and

Abstract

Objective

To determine whether pigs can be dually infected with different plaque variants of porcine reproductive and respiratory syndrome virus (PRRSV).

Animals

2 pregnant sows, 20 newborn pigs, and 20 three-week-old pigs.

Procedure

The 2 late-term pregnant sows were inoculated with the PRRSV small-plaque variant MN-Hs, and their pigs were challenge exposed at 7 days of age with the PRRSV large-plaque variant MN-HI. In addition, twelve 3-week-old pigs were inoculated with MN-Hs virus. Two groups of the pigs were challenge exposed with MN-HI virus at 14 and 42 days after initial inoculation. Virus was isolated from the pigs at various intervals, plaque sizes were examined, and serologic testing was performed.

Results

From the 2 groups of ten 7-day-old pigs, small-plaque PRRSV was isolated from 8 and 10 pigs. After subsequent challenge exposure, dual infections were diagnosed in 3 of 10 inoculated and 4 of 10 contact control pigs. In 3-week-old pigs infected with MN-Hs virus, dual infections were documented in 2 of 6 pigs when challenge exposed 14 days after initial infection. Virus was not isolated from sera of another 6 pigs challenge exposed 42 days after initial infection. Serum neutralization antibody was detected in all 6 pigs at challenge exposure.

Conclusions

Dual infections were documented in viremic newborn pigs and 3-week-old pigs, using 2 plaque variants of PRRSV. (Am J Vet Res 1997;58: 257–259)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine prevalence of intestinal chlamydial infection in pigs and to compare prevalence of diarrhea in infected pigs with that in noninfected pigs to evaluate the importance of Chlamydia sp as causes of diarrhea in pigs.

Animals and Procedures

Intestines from 351 sick pigs submitted to 2 veterinary diagnostic laboratories and from 96 healthy pigs that were part of an Escherichia coli susceptibility study were examined by immunoperoxidase staining for chlamydial antigen. The proportion of Chlamydia-infected pigs in each group was calculated and compared. The proportion of Chlamydia-infected pigs with diarrhea was compared with the proportion of noninfected pigs with diarrhea.

Results

15% of the sick and healthy pigs were infected with Chlamydia sp. Prevalence of diarrhea was equal between infected and noninfected pigs. Chlamydia sp were the third most common pathogens identified, and prevalence of chlamydial infection increased after 3 weeks of age.

Conclusions and Clinical Relevance

Intestinal chlamydiosis is common in commercial pigs, but most, if not all, infections are subclinical. Without collaborative evidence, simply identifying Chlamydia sp in feces or the intestinal tract of pigs with enteritis or diseases of other organ systems should not be considered proof that the organism caused the clinical signs of disease. (Am J Vet Res 1997;58:260–264)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate the safety and efficacy of avirulent live Salmonella choleraesuis strain 54 (SC54) as a vaccine to protect calves against salmonellosis caused by S dublin.

Animals

40 head of clinically normal 3 to 5-week-old male Holstein calves that were culture negative for Salmonella sp.

Procedure

Calves were randomly assigned to 4 test groups of 10 calves each. Group 1 received 8.5 × 107 colony-forming units (CFU) of SC54 SC. Groups 2 and 3 received 1.13 × 109 CFU of SC54, SC and intranasally, respectively. Group 4 received saline solution as a vaccine control. All calves were challenge exposed orally with 1.74 × 109 CFU of virulent S dublin 14 days after vaccination. Clinical signs and Salmonella shedding were monitored for 28 days after vaccination. Calves were necropsied, and organs were cultured for Salmonella sp 14 days after challenge exposure.

Results

Calves of groups 2 and 3 had slightly high rectal temperature after vaccination. Salmonella dublin challenge exposure resulted in mild clinical signs of salmonellosis. All vaccinated groups had significantly (P< 0.05) lower rectal temperature, fecal shedding of S dublin, and recovery of S dublin from organs after necropsy. SC54 was not recovered from fecal or blood samples collected after vaccination or from injection site samples or organs collected at necropsy.

Conclusions

SC54 given intranasally or SC to calves was safe and significantly (P < 0.05) reduced clinical signs and bacterial shedding after oral challenge exposure with S dublin.

Clinical Relevance

SC54 has potential as an effective vaccine to aid in prevention of salmonellosis caused by S dublin in calves. (Am J Vet Res 1997;58: 265–271)

Free access
in American Journal of Veterinary Research